Earthquakes and Maryland (2022)

Maryland's earthquake monitoring network is online. Visit the Seismic Network Pages for more information, and see live seismic displays.
You can download a PDF version of this brochure, suitable for printing.

By James P. Reger

INTRODUCTION

Earthquakes can be among the most devastating and terrifying of natural hazards. Although floods, tornadoes and hurricanes account for much greater annual loss in the United States, severe earthquakes pose the largest risk in terms of sudden loss of life and property. There are many interrelated factors that determine the extent of loss of property and life from an earthquake. Each of the following should be prefaced with "other factors being equal . . . ."

  • Amount of seismic energy released: The greater the vibrational energy, the greater the chance for destruction.
  • Duration of shaking: This is one of the most important parameters of ground motion for causing damage.
  • Depth of focus, or hypocenter: The shallower the focus (the point of an earthquake's origin within the earth), usually the greater the potential for destructive shock waves reaching the earth's surface. Even stronger events of much greater depth typically produce only moderate shaking at ground level.
  • Distance from epicenter: The potential for damage tends to be greatest near the epicenter (the point on the ground directly above the focus), and decreases away from it.
  • Geologic setting: A wide range of foundation materials exhibits a similarly wide range of responses to seismic vibrations. For example, in soft unconsolidated material, earthquake vibrations last longer and develop greater amplitudes, which produce more ground shaking, than in areas underlain by hard bedrock. Likewise, areas having active faults are at greater risk.
  • Geographic and topographic setting: This characteristic relates more to secondary effects of earthquakes than to primary effects such as ground shaking, ground rupture, and local uplift and subsidence. Secondary effects include landslides (generally in hilly or mountainous areas), seismic sea waves, or tsunamis (pretty much restricted to oceans and coastal areas), and fires (from ruptured gas lines and downed utility lines).
  • Population and building density: In general, risk increases as population and building density increase. Types of buildings: Wooden frame structures tend to respond to earthquakes better than do more rigid brick or masonry buildings. Taller buildings are more vulnerable than one- or two-story buildings when located on soft, unconsolidated sediments, but taller buildings tend to be the more stable when on a hard bedrock foundation.
  • Time of day: Experience shows there are fewer casualties if an earthquake occurs in late evening or early morning because most people are at home and awakeand thus in a good position to respond properly.

Although earthquakes have been the object of study and superstition for many centuries, the modern science of seismology really gained impetus after the famous San Francisco earthquake of 1906. Since then, geologists have learned much more about the structure and composition of the earth's interior and, more recently, have made progress in earthquake forecasting and in hazard and risk mitigation.

ORIGIN OF EARTHQUAKES

Most earthquakes occur when great stresses building up within the earth are suddenly released This sudden release of this stored energy causes movement of the earth's crust along fractures, called faults, and generates shock waves. These shock waves, or seismic waves, radiate in all directions from the focus, much as ripples radiate outward in two dimensions when a pebble is dropped into a pond.

The two basic types of seismic waves are body waves, or primary waves, which travel through the interior of the earth, and surface waves, which travel along the earth's surface and are believed to be responsible for most earthquake damage (Fig. 1).

There are two types of body waves: P waves, or primary waves, and S waves, or secondary waves. The faster moving P waves are compressional waves, and the slower S waves are shear waves. Compressional waves involve a "push-pull" vibration of earth material in the same direction as the P waves are moving. In contrast, shear waves "shake" material at right angles to their path. Differences in P- and S-wave characteristics have provided much information about the structure and composition of the earth's interior.

Although most earthquakes are associated with movement along faults, they can also be triggered by volcanic activity, by large landslides, and by some types of human activity. However, in areas not known for frequent earthquakes, pinpointing the cause of the rare tremor can be very difficult.

The theory of plate tectonics explains most earthquake occurrences. Ninetypercent or more of all earthquakes occur along boundaries between large, slowlymoving slabs, or plates, of the earth's crust and upper mantle, collectivelycalled the lithosphere. (For more background on plate tectonics, the readeris encouraged to refer to a recent introductory geology text or a good encyclopedia.)

Most earthquakes are shallow (0-40 miles to the focus), occurring in the lithosphere.The mechanism for most very shallow earthquakes probably involves fracturingof brittle rock in the crust or relief of internal stresses due to frictionalresistance locking opposite sides of a fault.

Very little is known about the causes of earthquakes in the eastern UnitedStates. In general, there is no clear association among seismicity, geologicstructure, and surface displacement, in contrast to a common association inthe western U.S.

The mid-Atlantic and central Appalachian region, including Maryland, is characterizedby a moderate amount of low-level earthquake activity, but their cause or causesare largely a matter of speculation. In Maryland, for example, there are numerousfaults, but none is known or suspected to be active. Because of the relativelylow seismic energy release, this region has received relatively little attentionfrom earthquake seismologists (Bollinger, 1969).

In the Atlantic Coastal Plain, it is now thought that earthquakes may be associatedwith nearly vertical faults that formed during the opening of the present AtlanticOcean during the Triassic period about 220 million years ago (Hanks, 1985).Such faults would occur in the "basement" bedrock, and not in theoverlying, younger Coastal Plain sediments themselves.

(Video) Earthquakes in Maryland?

Recent evidence suggests that earthquakes in the Valley and Ridge Provinceand in the Piedmont Province occur at shallow depths (usually less than 15miles) in the Precambrian crystalline basement rocks (Wheeler and Bollinger,1984). The geologic structure that may be responsible for earthquake activityin these areas is a nearly horizontal fault that formed during continentalcollision and closing of a proto-Atlantic Ocean during late Paleozoic timeapproximately 300 million years ago. It is also possible that some earthquakesin the Piedmont are in some way related to igneous dikes that were intrudedinto surrounding bedrock during the Triassic and Jurassic periods (roughly200-175 million years ago).

MEASURING EARTHQUAKES
The vibrations produced by earthquakes are detected and recorded by instrumentscalled seismographs. The time of occurrence, the duration of shaking, the locationsof the epicenter and focus, and estimates of the energy released can be obtainedfrom data from seismographs set up around the world.

TABLE 1. The Modified Mercalli Intensity Scale of 1931 (abridged). I Not feltexcept by very few people under especially favorable conditions. II Felt bya few people, especially those on upper floors of buildings. Suspended objectsmay swing. III Felt quite noticeably indoors. Many do not recognize it as anearthquake. Standing motorcars may rock slightly. IV Felt by many who are indoors;felt by a few outdoors. At night, some awakened. Dishes, windows and doorsrattle. V Felt by nearly everyone; many awakened. Some dishes and windows broken;some cracked plaster; unstable objects overturned. VI Felt by everyone; manyfrightened and run outdoors. Some heavy furniture moved; some fallen plasteror damaged chimneys. VII Most people alarmed and run outside. Damage negligiblein well constructed buildings; considerable damage in poorly constructed buildings.VIII Damage slight in speciall designed structures; considerable in ordinarybuildings; great in poorly built structures. Heavy furniture overturned. Chimneys,monuments, etc. may topple. IX Damage considerable in specially designed structures.Buildings shift from foundations and collapse. Ground cracked. Undergroundpipes broken. X Some well-built wooden structures destroyed. Most masonry structuresdestroyed. Ground badly cracked. Landslides on steep slopes. XI Few, if any,masonry structures remain standing. Railroad rails bent; bridges destroyed.Broad fissure in ground. XII Virtually total destruction. Waves seen on ground;objectsthrown into the air. In 2002, a seismograph station was established at SoldiersDelight in Baltimore County. A live link to the station is at http://www.mgs.md.gov/seismic/index.shtml.The station is a cooperating partner in the Lamont Doherty Earth ObservatorySeismic Network of Columbia University, along with stations in Delaware andPennsylvania. Other regional seismograph stations are in State College, Pennsylvania;Morgantown, West Virginia; and Blacksburg, Virginia.

TABLE 2. Approximate relationships among earthquake magnitude,intensity, worldwide occurrence, and area affected (after U.S. GeologicalSurvey, 1981, 1989).
General
Description
Richter
Magnitude
Modified
Mercalli
Intensity
Expected
Annual
Incidence
Distance
Felt
(miles)
Microearthquakebelow 2.0--600,000--
Perceptible2.0-2.9I--II300,000--
Felt generally3.0-3.9II-III49,00015
Minor4.0-4.9IV-V6,00030
Moderate5.0-5.9VI-VII1,00070
Large (Strong)6.0-6.9VII-VIII120125
Major (Severe)7.0-7.9IX-X18250
Great8.0-8.9XI-XII1.1450

Measurement of the severity of an earthquake can be expressed in several ways,the two most common being intensity and magnitude. The intensity, reportedon the Modified Mercalli Intensity (MMI) Scale, is a subjective measure interms of eyewitness accounts (Table 1). Intensities are ranked on a 12-levelscale and range from barely perceptible (I) to total destruction (XII). Thelower intensities are described in terms of people's reactions and sensations,whereas the higher intensities relate chiefly to observable structural damage.

Magnitude is an objective measure of earthquake severity and is closely relatedto the amount of seismic energy released at the focus of an earthquake. Itis based on the amplitude of seismic waves as recorded on standardized seismographs.The standard for magnitude measures is the Richter Scale, an open-ended scaleexpressed in whole numbers and decimal fractions. The Richter Scale is logarithmic,meaning that an earthquake of magnitude 5.0 has 10 times the wave amplitudeof a magnitude 4.0 and 100 times the ground vibration amplitude of a magnitude3.0 event. As a first approximation, each whole number increment on the RichterScale corresponds to a release of about 31 times more seismic, or vibrational,energy. Actually, there are several different methods of determining Richtermagnitude. One uses surface waves, another body waves, and so on. However,the differences in results are slight.

Although the Richter scale has no upper limit, the greatest magnitude on recordis 8.9 for earthquakes that occurred off the northwest coast of South Americain 1906 (magnitude estimated) and off the east coast of Honshu, Japan in 1933.By comparison, the famous San Francisco earthquake of 1906 had an estimatedmagnitude of about 8.3 and an MMI of X.

A comparison of the Modified Mercalli and the Richter Scales is shown in Table2. It is important to realize that these relationships are only generalizationsand can vary for any given earthquake depending upon local geologic conditions.As a general rule of thumb, damage is slight at the magnitude 4.5 level, becomesmoderate at about 5.5, and above 6.5 or so can range from considerable to nearlytotal (Bollinger et al., 1989). This rela tion may not apply to earthquakesin Maryland, if recent events are any indication. A small tremor in January,1990, west of Baltimore was assigned an Modified Mercalli Intensity V nearthe epicenter, but registered only a 2.5 to 2.6 magnitude on the Richter scale.

EARTHQUAKES IN AND AROUND MARYLAND

To most people in the United States, damaging earthquakes are a Californiaphenomon, but this is misleading. Even though the greatest seismicity in theUnited States occurs along the Pacific Coast (especially Alaska and SouthernCalifornia), major earthquakes have also occurred in the central and easternU.S.

The last earthquake to cause appreciable damage in the eastern United Statesoccurred in 1886 near Charleston, South Carolina. It had an estimated magnitudeof 6.5-7, an intensity of X, and was felt over an area of two million squaremiles. Even in Maryland, the felt intensity from this earthquake was IV toV.

Perhaps the greatest seismic event ever to occur in North America in historictimes was a series of earthquakes that shook the mid-continent around New Madrid,Missouri in the winter of 1811-1812. Estimates of the magnitude range as highas 8.7; estimated maximum intensity was XII; and the felt area, which includedMaryland, was 2 million square miles.

Other damaging earthquakes in the eastern U.S. include an intensity VIII eventnear Boston in 1755 and intensity VI events near New York City in 1737 and1884.

Figure 2 shows earthquake epicenters in the eastern United States and easternCanada for a 10-year period, 1976-1985. Although numerous, these earthquakeswere all low-intensity, low-magnitude events. Most had a magnitude less than2.0. It is definitely worth noting that Maryland seems to be part of a seismicallyquiet zone.

Several earthquakes in adjacent states have been felt in Maryland. Marylandersare more likely to feel one of these out-of-state earthquakes than one withinMaryland. As shown by Figure 2, Southwestern Virginia, central Virginia, andthe Atlantic seaboard northward from Wilmington, Delaware have significantlymore seismic activity than does Maryland. One out-of-state earthquake thatwas felt in much of Maryland occurred Easter Sunday, April 22, 1984. In fact,it was reported felt in eight states and the District of Columbia, over anarea of approximately 19,000 square miles. Centered about 12 miles south ofLancaster, Pennsylvania, this earthquake registered 4.1 on the Richter Scaleand had an epicentral intensity of V to VI. Most notable effects in Marylandwere in the northeastern part of the state, which generally experienced ModifiedMercalli Intensity V effects for example, hanging pictures fell in Conowingo;windows cracked in Elkton and Joppa; and standing vehicles rocked slightlyin Union Bridge (Stover, 1988). A 3.0-magnitude tremor four days earlier isconsidered to have been a foreshock. Ten aftershocks registering 2 to 2.5 Richtermagnitude occurred over a four-day period after the April 22 event. The Lancasterearthquake is likely related to Triassic-age structures in the area.

As of late 1993, 47 earthquakes had been reported within Maryland’sborders (Table 3 and Fig. 3). Over the next ten years, that total reached 61.(For a frequently updated list and map of Maryland earthquakes, go to the MarylandGeological Survey’s FactSheet 13. The accuracyand precision of these epicenter determinations is such that a few of the closerout-of-state earthquakes could have occurred within Maryland and some of thosenear the state’s boundaries may actually have occurred in adjacent states.For example, not included in the list was a moderate shock that occurred onJanuary 2, 1885 in an area near the Frederick County, Maryland-Loudon County,Virginia border. The maximum intensity was V, with the total felt area coveringmore than 3,500 square miles. Of the Maryland earthquakes, 2 occurred in theValley and Ridge Province, 36 were in the Piedmont Province, and 10 were inthe Coastal Plain Province.

(Video) Largest earthquake recorded in Maryland

The first reported earthquake to have actually had its epicenter in Marylandoccurred south of Annapolis on April 25, 1758, but no record of its strengthis known to exist. The shock lasted 30 seconds and was preceded by subterraneannoises. Additional felt reports were received from a few points in Pennsylvania(U.S. Geological Survey, 1973). Maryland's strongest confirmed tremor was a3.1-magnitude event near Hancock, Washington County, in 1978. That perhapswas rivaled by an intensity V event (unknown magnitude) near Phoenix, BaltimoreCounty, in 1939. Earthquakes of such magnitudes or intensities are still consideredto be minor, and very seldom result in significant damage or injury.

FIGURE 3. Map showing approximate epicenters of historic earthquakes in and near Maryland since 1758

Table 3: Earthquake chronology of Maryland, 1758-2003.The numbers 1-61 refer to those on the map in Figure 3. (Data for 1758-1979compiled primarily by the U.S. Geological Survey (USGS);1990-1993 datafrom Delaware Geological Survey (DGS), Lamont-Doherty Earth Observatory(LDEO), and USGS; 1996 to 2002 data from DGS, LDEO, Virginia PolytechnicInstitute (VPI)., and Maryland Geological Survey.
No.Date (UTC) 1
Year Mo. Day
Time
(UTC) 1
(hh:mm:ss)
Epicenter 2 General Location Depth (km) Intensity 3 Magnitude4
N Lat (deg.) W Lon (deg.)
1 1758 04 25 02:30 38.90 -76.50 Annapolis ... V (3.5, 3.7)
2 1828 02 24 ... 38.90 -76.70 Bowie ... ... ...
3 1876 01 30 02:05 38.90 -76.50 Annapolis ... ... ...
4 1876 04 10 ... 38.50 -76.60 Prince Frederick ... III (2.7)
5 1877 09 01 16:00 38.70 -76.80 Brandywine ... III (2.7)
65 1815 01 04 08:005 39.57 -77.00 Westminster ... IV-V (3.1)
7 1883 03 11 23:57 39.50 -76.40 Fallston ... IV (3.1, 3.3)
8 1883 03 12 05:00 39.50 -76.40 Fallston ... III (2.7, 2.9)
9 1902 03 10 05:00 39.60 -77.20 Union Bridge ... III (2.7)
10 1902 03 11 10:30 39.60 -77.20 Union Bridge ... III (2.7)
11 1903 01 01 17:30 39.60 -77.20 Union Bridge ... III (2.7)
12 1903 01 01 22:45 39.60 -77.20 Union Bridge ... II (2.4)
13 1906 10 13 15:00 39.20 -76.70 Catonsville ... III (2.7)
14 1910 01 24 02:20 39.60 -77.00 Westminster ... II (2.4)
15 1910 04 24 02: 39.20 -76.70 Catonsville ... III (2.7)
16 1928 10 15 ... 38.30 -75.10 Ocean City ... IV (2.7, 3.3)
17 1930 11 01 06:34 39.10 -76.50 Round Bay - Severna Park ... IV (3.1, 3.3)
18 1930 11 01 07:02 39.10 -76.50 Round Bay - Severna Park ... III (2.7)
19 1939 06 22 23:10 39.50 -76.60 Phoenix ... III (2.7)
20 1939 11 18 02:33 39.50 -76.60 Phoenix ... IV (3.1)
21 1939 11 26 05:20 39.50 -76.60 Phoenix ... V (3.5, 3.7)
22 1962 09 07 14:00 39.70 -78.20 Hancock 38 IV (3.3)
23 1978 04 26 19:30 39.7 -78.24 Hancock 15 ... 3.10
24 1986 05 23 17:48 38.69 -77.04 Accoceek - Piscataway 0.20 ... 2.5
25 1990 01 13 20:48 39.36 -76.80 Randallstown (V), Eldersburg (IV), Ellicott City (IV), Granite(IV), Owings Mills (III) 3-5 V 2.6 2.5
26 1990 04 04 16:15 39.35 -76.78 Granite - Randallstown - Baltimore 7.0 10.0 II 1.7
27 1991 09 28 11:28 39.36 -76.83 Granite - Randallstown 5.0 III 2.4
28 1993 03 10 14:32 39.2 -76.8 Columbia (IV) - Ellicott City (II) - Fulton (II) 5.0 II-IV 2.5
29 1993 03 12 00:54:00 39.19 -76.87 Columbia - Allview Estates 5.0 II-III 2.0
30 1993 03 15 04:30 39.19 -76.87 Columbia - Allview Estates - Laurel 0.9 III-V 2.7
31 1993 03 16 07:59:00 39.19 -76.87 Columbia - Allview Estates 5.0 II-III 1.8
32 1993 03 16 16:59 39.19 -76.87 Columbia - Allview Estates 5.0 II-III 1.8
33 1993 03 17 11:54 39.19 -76.87 Columbia - Allview Estates 0.5 I-II =/< 1.0
34 1993 03 19 05:50 39.19 -76.87 Columbia - Allview Estates 0.5 I-II 1.0
35 1993 03 19 19:26 39.19 -76.87 Columbia - Allview Estates 0.5 I <1.0
36 1993 03 21 10:55 39.47 -76.30 Aberdeen - Bel Air ... I-II 1.5
37 1993 03 22 10:26 39.19 -76.86 Columbia - Allview Estates 0.5 not felt about 0.0
38 1993 03 26 14:03 39.28 -76.82 Ellicott City near jct US40 & 29 ... I-II <1.5 (est.)
39 1993 04 04 17:32 39.19 -76.87 Columbia - Allview Estates 0.5 I-III 1.5
40 1993 04 04 17:33 39.19 -76.87 Columbia - Allview Estates 0.5 I-II 1.5
41 199304 08 09:10 39.19 -76.87 Columbia - Allview Estates 0.5 I-II 1-1.5
42 1993 07 09 06:31 39.19 -76.87 Columbia - Allview Estates 0.5 (est.) II-III 1.9
43 1993 07 12 21:24 39.19 -76.87 Columbia - Allview Estates 0.5 (est.) III-IV 2.1
44 1993 10 28 06:00 39.25 -76.77 Ilchester - Ellicott City ... IV 2.1
45 1993 10 28 06:01 39.25 -76.77 Ilchester - Ellicott City ... IV 1.8
46* 1993 11 17 16:35 39.19 -76.87 Columbia - Allview Estates 0.5 (est.) III 1.7 (est.)
47* 1993 11 27 15:26 39.19 -76.87 Columbia - Allview Estates ... I-II <1.5 (est.)
48* 1993 11 27 18:43 39.19 -76.87 Columbia - Allview Estates ... I-II about 1.5 (est.)
49 1994 10 28 02:04 39.1 -76.60 Glen Burnie - Pasadena -Gambrills -Millersville ... IV 2.7
50 1996 08 02 07:19 39.57 -76.08 Perryville ... II-III 2.2
51 1996 10 17 11:43 39.7 -76.07 Rising Sun (epicenter may be in Pennsylvania) 5.4 IV 2.2, 2.3
52-54 1996 12 06 3 very small events in 35 min. 39.19 -76.87 Columbia - Allview Estates ... II <1.5 (est.)
55-57 199612 14 3 very small events in 75 min. 39.19 -76.87 Columbia - Allview Estates ... II <1.5 (est.)
586 1996 12 16 15:10 39.25 -76.77 Ilchester - Ellicott City ... I about 1 (est.)
59 1996 12 22 05:56 39.19 -76.87 Columbia - Allview Estates

5

III 2.0, 2.3
602001 12 18...39.19-76.84Columbia nr US29-Md32...II1.5-2.0 (est)
612002 03 22...39.19-76.84Columbia nr US29-Md32...I1-2 (est.)
622003 12 09 20:59:1437.599-77.90028 miles west of Richmond in rural Powhatan County, VA4.8VI4.5
632005 02 23 14:22:4339.26-76.58SE Baltimore near Fort McHenry, Dundalk, Glen Burnie, Pasadena, Gambrills...VI2.0-2.1
642008 12 27 05:04:3440.114-76.4039 km (6 miles) W of Lancaster, PA.4IV3.4
652009 07 01 13:44:4339.64-75.48Southwestern New Jersey5III2.8
662009 09 29 13:58:5139.607-76.3427 km (4 miles) NNE (15°) from Bel Air North, MD5II1.6
672010 07 16 09:04:4739.17-77.25Potomac-Shenandoah Region, MD 5V3.4
682011 08 23 17:51:0437.936-77.9338 km (5 miles) SSW (195°) from Mineral, VA6V-VI5.8
692017 10 3000:34:3139.279-77.051Glenelg, Maryland2I1.52
702017 11 1115:55:4439.261-77.0390.8 km (0.5 mi) ESE of Roxbury, Maryland4I1.5

NOTES:
* Probable, but not confirmed by seismographs in the region. Magnitudeestimated from other events in the series.

  1. Time (UTC): Coordinated Universal Time. For the Eastern timezone, subtract 5 hours from UTC time for Eastern Standard Time, 4 hoursfor Eastern Daylight Saving Time. For example: 1200 UTC(noon) = 0800, or 8:00 am EDT = 0700, or 7 am EST. Note that00:00-04:59 UTC converts to 1800-23:59 of the previous day.
  2. Epicenter, as calculated from seismograph stations =data and/orestimated by the Maryland Geological Survey on the basis of felt reports;1962 marked the first instrumentally determined epicenter.
  3. Except for event #6 in 1881 (see note 5 below), pre-instrumental(pre-1962) intensity estimates are earthquake catalogs published byvarious seismograph networks.
  4. Except for event #6 in 1881 (see note 5 below) pre-instrumental magnitudeestimates (shown in parentheses) by L. Seeber and J. Armbruster (LamontDoherty Earth Observatory of Columbia University) and/or M. Chapman(Virginia Tech Seismological Observatory); magnitude estimates fora large number of pre‑instrumental earthquakes in the regionwere derived using the region-specific relationships between felt area,maximum intensity and mb(Lg) magnitude developed by Sibol et al. (1987). Subsequentmagnitudes are from instrumental measurements.
  5. Event #6 has not been listed in any previously published earthquakelist. A rather detailed account of this event appeared in theJanuary 8, 1881 edition of the American Sentinel newspaper. Estimatesof the epicenter and intensity have been made on the basis of the newspaperdescriptions; magnitude estimates based on Sibol et al. (1987).
  6. The Delaware Geological Survey states that this event may have beena sonic boom instead of an earthquake (S. Baxter, oral commun., Aug.16, 2001).

Recent confirmed earthquakes in Maryland were both felt in roughly the samelocation and, therefore, may possibly be related. The first of these occurredon January 13, 1990 at about 3:48 p.m. local time (EST). According to reportsfrom nine seismograph stations, the shock's magnitude registered 2.5 to 2.6on the Richter scale. Depth to focus was approximately 2 miles, which indicatesa very shallow earthquake. Intensities ranged from MMI V in the Randallstownarea; to IV at Eldersburg, Ellicott City, Granite and Woodstock; and III atOwings Mills. Several first-hand accounts of the event from the Granite-Hernwoodarea reported that houses shook or windows rattled, both indicative of an intensityIV. No damage was reported.

On April 4, 1990, reports of another small earthquake came from the Randallstown-Granite-Hernwoodarea. However, seismic stations in Delaware and Virginia place the epicenterin western Carroll County (Fig. 4), approximately 20 miles west of the Randallstownarea. By all accounts, this event was smaller than the January tremor. Preliminaryanalysis of seismic records indicated a magnitude of about 1.6 or 1.7, andfirst-hand accounts of a few local residents suggested a Mercalli intensityof about II or III. One eyewitness described the event as starting with thesound of distant thunder, getting louder for about 25 seconds, then followedby 5 to 7 seconds of minor rumbling or shaking. Another resident of this areahas reported nearly two dozen similar events, although not confirmed as earthquakes,between October, 1987 and May, 1990.

ASSESSING THE RISK

The earthquake hazard in the United States has been estimated in a varietyof ways. Chief among them is the production of "risk maps." Suchmaps prove useful in establishing building codes, engineering design standards,and insurance rates in areas of high risk. Seismic risk maps are based eitheron relative risk or on the probability of a certain seismic event at a particulartime and place.

Two examples of risk maps are shown in Figure 4. Figure 4a shows four zonesthat are assigned risk on a relative scale. This map is based on the knownoccurrence of damaging earthquakes in the past, evidence of strain release,and consideration of major geologic structures and provinces believed to beassociated with earthquake activity.

For years, this map was widely used, because it was the best risk map available.However, this type of risk map has several drawbacks. For one thing, it doesnot consider frequency of occurrence. Furthermore, there is no justificationfor assuming that events larger than those observed historically, especiallyin the East, will not occur in the future. It is also known that ground-motionattenuation ("dying out" of the shock waves) with distance is farless in the eastern U.S. than in the western states. Felt areas are, in general,one order of magnitude greater in the East than for similar earthquakes inthe West (Bollinger, 1973). Nonetheless, according to this map, Maryland isappropriately placed into a zone of minor expected damage, corresponding toMercalli intensity V to VI.

A more recent development that is still being improved upon is the probabilisticmap. One example is illustrated in Figure 4b. This particular map shows theexpected maximum horizontal ground acceleration (as a percentage of g, theacceleration due to gravity, 32.2 ft/sec2) on rock sites. These ground accelerations,which are one measure of ground shaking, have a 90-percent probability of notbeing exceeded in 50 years. This is equivalent to a recurrence interval, orreturn period, of 475 years (Hays, 1980).

Damage begins to occur at about 10-15% g. Below 4% g, which is the lowestcontour on this map, shaking effects are controlled by earthquakes of magnitude4.0 or less in other words, minor earthquakes. An acceleration of 0.1% g ormore is perceptible to people (Algermissen and Perkins, 1976). According toFigure 4b, Maryland has a very low chance of experiencing a damaging earthquakein a 50-year period. For moderate exposure times (10-100 years), the expectedground motion associated with earthquakes in this region would be of marginalinterest (Algermissen et al., 1982). As a rough estimate, Maryland's fallingin the 4-10% g category on the map in Figure 4b might translate into a maximumexpected magnitude of 4.0-4.5. It is important to emphasize that these figuresare only rough estimates. The difficulty in assigning maximum magnitudes ismost acute where no faults are known, where seismicity is low, and where near-maximumearthquakes may not have occurred in historical times. This is true for mostof the eastern United States (Algermissen and Perkins, 1976).

Downloads and Links

Earthquakes and Maryland (5)Educational Series 9: Earthquakes and Maryland (pdf, 1.1 MB)

Earthquakes and Maryland (6)Fact Sheet 13: Summary of Maryland Earthquakes, 1758-2000 (pdf, 334 kB)

(Video) Earthquake strikes Maryland

Maryland Geological Survey's SeismicNetwork

Open File Report 99-03-1: Earthquake Hazard Maps for Maryland

REFERENCES CITED

Algermissen, S. T., 1969, Seismic risk studies in the United States:Proc., 4th World Conference on Earthquake Engineering, Santiago, Chile,v. 2, p. 14-27.

Algermissen, S. T. and Perkins, D. M., 1976, Probabilistic estimateof maximimum acceleration in rock in the contiguous United States: U.S.Geol. Survey Open-File Report 76-416, 45 p.

Algermissen, S. T., Perkins, D. M., Thenhaus, P. C., Hanson, S. L.and Bender, B. L., 1982, Probabilistic estimates of maximum accelerationand velocity in rock in the contiguous United States: U. S. Geol. SurveyOpen-File Report 82-1033, 99 p.

Bollinger, G. A., 1969, Seismicity of the Central Appalachian statesof Virginia, West Virginia, and Maryland1758-1968: Seismol. Soc. AmericaBull., v. 59, no. 5, p. 2103-2111.

_______, 1973, Seismicity of the southeastern United States: Seismol.Soc. America Bull., v. 63, no. 5. p. 1785-1808.

Bollinger, G. A., Snoke, J. A., Chapman, M. C., and Sibol, M. S.,1989, Estimates of the occurrence and resulting effects of damaging earthquakesin Virginia: Virginia Minerals, v. 35, no. 3, p. 17-22.

Foley, J. E., Doll, C., Filipkkowski, F., and Lorsbach, G. (eds.),1985, Seismicity of the Northeastern United States, April 1-June 30, 1984:Weston Observatory, Boston College, Northeastern U.S. Seismic Network Bull.35, 40 p.

Hanks, T. C., 1985, The National Earthquake Hazards Reduction ProgramScientificStatus: U.S. Geol. Survey Bull. 1059, 40 p.

Hays, W. W., 1980, Procedures for estimating earthquake ground motions:U.S. Geol. Survey Prof. Paper 1114, 77p.

Sibol, M. S., Bollinger, G. A., and Mathena, E. C. (eds.), 1985,Seismicity of the Southeastern United States, January 1-January 30, 1985:Seismological Observatory, Virginia Polytechnic Institute and State University,Southeastern U.S. Seismic Network Bull. 16, 70 p.

(Video) Earthquake Begins in Virginia, Rattles East Coast

Spence, W., Sipkin, S. A., and Choy, G. L., 1989, Measuring the sizeof an earthquake: Earthquakes and Volcanoes, U.S. Geological Survey, v.21, no. 1, p. 58-63.

Stover, C. W., 1988, United States Earthquakes, 1984: U.S. GeologicalSurvey Bulletin 1862, 179 p.

Stover, C. W., Reagor, B. G., and Algermissen, S. T., 1984, UnitedStates Earthquake Data File: U.S. Geological Survey Open-File Report 84-225,123 p.

U.S. Geological Survey, 1973, Earthquake history of Maryland: EarthquakeInformation Bulletin, v. 5, no. 4, p. 22-23.

_______, 1981, Questions and answers: Earthquake Information Bulletin,v. 13, no. 4, p. 153-154.

_______, 1990, Preliminary Determination of Epicenters, Weekly Listing:National Earthquake Info. Center, Denver, No. 2-90, Feb. 1, 1990.

Wheeler, R. L. and Bollinger, G. A., 1984, Seismicity and suspectterranes in the Southeastern United States: Geology, v. 12, no. 6, p. 323-326.

SUGGESTED READINGS FOR THE NON-GEOLOGIST

Bolt, B. A., 1978, Earthquakes, a primer: W. H. Freeman and Co., SanFrancisco, 241 p.

Gere, J. M. and Shah, H. C., 1984, Terra non firma: W. H. Freemanand Co., San Francisco, 203 p.

Halacy, D. S., Jr., 1974, Earthquake A natural history: Bobbs-MerrillCo., New York, 162 p.

Hodgson, J. H., 1964, Earthquakes and earth structure: Prentice-Hall,Inc., Englewood Cliffs, N.J., 166 p.

Pakiser, L. C., 1988, Earthquakes: U.S. Geological Survey, Denver,Colo., 20p.

(Video) Virginia earthquake: videos capture the moment tremors hit U

This pamphlet was prepared by James P. Reger.
Compiled by the Maryland Geological Survey, 2300 St. Paul Street, Baltimore, MD 21218
This electronic version of "Earthquakes and Maryland " was prepared by Bob Conkwright, Division of Coastal and Estuarine Geology, Maryland Geological Survey.

FAQs

Is Maryland an earthquake prone area? ›

Even though our area is subject to earthquakes on an infrequent basis, some areas of Maryland are at moderate risk for earthquakes.

Did an earthquake just happen Maryland? ›

There were no significant confirmed earthquakes in or near Maryland in the past 24 hours.

Is there a fault line in Maryland? ›

While the Maryland Geological Survey cites numerous fault lines in the state, director Richard Ortt explains that East Coast faults are not the same as the tectonic plate faults like on the West Coast. “We don't have plates moving under one another,” Ortt said. “We have something called intra-plate faults.

In what year did an earthquake hit Maryland? ›

BALTIMORE (WJZ) -- Ten years ago today, the Earth moved and grabbed the attention of millions of people in Maryland and the Mid-Atlantic. A rare 5.8 magnitude earthquake shook Maryland on Aug. 23, 2011. The U.S. Geological Survey said the earthquake was half a mile deep.

Could there be a tsunami in Maryland? ›

A tsunami is just as likely to hit Maryland as it is the Bahamas or Florida.

When was the last tsunami in Ocean City Maryland? ›

M4. 6 - Ocean City, Maryland
Magnitude4.6 - Richter scale
LocationOcean City, Maryland (217km SE) LAT 37.2114, LON -73.0694
Date-TimeJan 15, 2019 23:30:48 UTC Jan 15, 2019 18:30:48 UTC -05:00 at epicenter
SourceUSGS NEIC (WDCS-D)
Event ID(s)us2000j4bf
2 more rows
15 Jan 2019

How often is Maryland earthquakes? ›

Maryland has been the epicenter of a felt earthquake 66 times since 1758. This equates to about one earthquake every three years.

What was the worst earthquake in Maryland? ›

Maryland's strongest confirmed tremor was a 3.1-magnitude event near Hancock, Washington County, in 1978.

Has Baltimore ever had an earthquake? ›

Since the 2011 earthquake, Marylanders have experienced much smaller ones. According to the MGS, there is, on average, an earthquake in Maryland once every three years. A 5.8 magnitude earthquake centered in Virginia was felt in the greater Baltimore area 10 years ago Monday.

What tectonic plate is Maryland on? ›

Maryland, and the entire east coast of the United States, is solidly within the North American Plate. Earthquakes can and do occur within tectonic plates, but it is nowhere near as common as an earthquake occuring along the boundaries of tectonic plates, Vanko says.

What magnitude was the earthquake in Maryland? ›

A 2.1-magnitude earthquake struck near Clarksville, Md., early Wednesday according to the United States Geological Survey. There were no reports of damage or injuries from the quake in Howard County that occurred at around 2:10 a.m. People took to Twitter to report they felt shaking in a broader area.

Is there a major fault line on the East coast? ›

Answer and Explanation: Yes, there are fault lines that run through the east coast of the United States. Though these faults are older and less active than those on the west coast of the country they can still produce earthquakes.

Did Columbia MD just have an earthquake? ›

Felt a quake? Report it! Show quakes near me! There were no significant confirmed earthquakes in or near Columbia in the past 24 hours.

Was there an earthquake in DC today? ›

There were no significant confirmed earthquakes in or near Washington DC in the past 24 hours.

What does a tiny earthquake feel like? ›

A small earthquake nearby will feel like a small sharp jolt followed by a few stronger sharp shakes that pass quickly. A small earthquake far away will probably not be felt at all, but if you do feel it, it will be a subtle gentle shake or two that is easier to feel if you're still and sitting down.

How far inland would a mega tsunami go? ›

Waves of this type are called Mega Tsunami. They are so great that they can reach several hundred meters in height, travel at the speed of a jet aircraft and get up to 12 miles (20 Kilometers) inland.

How far inland will a tsunami go? ›

Tsunami waves can continously flood or inundate low lying coastal areas for hours. Flooding can extend inland by 300 meters (~1000 feet) or more, covering large expanses of land with water and debris.

Has the Chesapeake Bay ever had a tsunami? ›

When intense storms moved through the Chesapeake region on Monday afternoon and evening, a weather phenomenon occured in the Bay: a tsunami. Yes, you read that right: The National Weather Service Mount Holly office says a rare meteotsunami happened in the Chesapeake Bay near Tolchester Beach.

What's happen in Maryland tsunamis? ›

Rare Tsunami Formed In Chesapeake Bay During Monday's ... - YouTube

Has a tsunami ever hit Virginia Beach? ›

Tsunamis have struck the western edge of the Atlantic Ocean, north and south of Norfolk/Virginia Beach.

Was there an earthquake in Ocean City Maryland? ›

The U.S. Geological Survey (USGS) confirms a 4.7 magnitude earthquake was detected in the Atlantic Ocean, off the coast of Ocean City, Maryland, at 6:30 p.m. Tuesday. According to USGS, the earthquake was centered 136 miles east-southeast of Ocean City.

What was that loud boom today 2021 Maryland? ›

A loud boom and shaking heard and felt by hundreds of residents across New Castle County Wednesday morning – which scientists initially said was an earthquake – was likely caused by a Maryland explosion, scientists now say.

Was there an earthquake in Virginia last night? ›

There were no significant confirmed earthquakes in or near Virginia, USA in the past 24 hours.

Is there a fault line in Delaware? ›

Delaware Earthquake a Head-Scratcher for Seismologists; No Known Fault Line Where Tremor Occurred.

What is the Richter scale? ›

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.

Which process is most likely to produce a volcano with gentle slopes? ›

Shield volcanoes

Where a volcano produces low viscosity, runny lava, it spreads far from the source and forms a volcano with gentle slopes: a shield volcano. Most shield volcanoes are formed from fluid, basaltic lava flows. Mauna Kea and Mauna Loa are shield volcanoes.

Was there an earthquake in Essex today? ›

There were no significant confirmed earthquakes in or near Essex in the past 24 hours.

What are the 5 geologic areas in Maryland? ›

Maryland is made up of six physiographic provinces, or regions where the geology and climate make the land different from adjacent areas. These provinces include the Appalachian Plateaus; Ridge and Valley; Blue Ridge; Piedmont; Atlantic Coastal Plain; and the Atlantic Continental Shelf.

Is North America Moving? ›

The North American plate is moving to the west-southwest at about 2.3 cm (~1 inch) per year driven by the spreading center that created the Atlantic Ocean, the Mid Atlantic Ridge.

Where do most earthquakes occur? ›

Over 80 per cent of large earthquakes occur around the edges of the Pacific Ocean, an area known as the 'Ring of Fire'; this where the Pacific plate is being subducted beneath the surrounding plates. The Ring of Fire is the most seismically and volcanically active zone in the world.

Could a tsunami hit the east coast of the United States? ›

Although the risk is small, tsunamis are possible on the East Coast of the United States from a variety of sources, according to new research. And as Hurricane Sandy showed, the region is completely unprepared for a major influx of water, said U.S. Geological Survey researcher Uri ten Brink.

Has the East Coast ever had an earthquake? ›

1) Severe earthquakes have occurred in the eastern U.S.:

In November of 1755, an earthquake with an estimated magnitude of 6.0 and a maximum intensity of VIII occurred about 50 miles northeast of Boston, Massachusetts.

Which two states have the least number of earthquakes? ›

Florida and North Dakota are the states with the fewest earthquakes. Antarctica has the least earthquakes of any continent, but small earthquakes can occur anywhere in the World.

Can you feel a 2.1 earthquake? ›

Normally, earthquakes below magnitude 3 or so are rarely felt. However, smaller quakes from magnitude 2.0 can be felt by people if the quake is shallow (few kilometers only) and if people are very close to its epicenter and not disturbed by ambient factors such as noise, wind, vibrations of engines, traffic etc.

Was there an earthquake in Pennsylvania today? ›

Felt a quake? Report it! Show quakes near me! There were no significant confirmed earthquakes in or near Pennsylvania in the past 24 hours.

How often are earthquakes in DC? ›

Approximately 10 to 15 earthquakes are recorded annually in South Carolina with 3 to 5 of them felt or noticed by people. About 70 percent of South Carolina earthquakes are located in the Middleton Place-Summerville Seismic Zone.

How many earthquakes were there in 2021? ›

The year 2021 was a very active period for global seismicity, with 19 major earthquakes, three of which were over 8.0, and was also the most seismically active since 2007. There were a total of 2,476 fatalities, with the majority from a M 7.2 in Haiti.

What are the signs of a big earthquake coming? ›

A good prediction must indicate when and where an earthquake will take place. Fault segments behave the same way over time. Signs that an earthquakes may occur include foreshocks, ground tilting, water levels in wells, and the relative arrival times of P- and S-waves.

Why is a doorway safe place during an earthquake? ›

DO NOT stand in a doorway. You are safer under a table. In modern houses, doorways are no stronger than any other part of the house. Doorways do not protect you from the most likely source of injury − falling or flying objects.

What will you do once the earthquake stops? ›

What to Do After an Earthquake. Check yourself and others for injuries. Provide first aid for anyone who needs it. Check water, gas, and electric lines for damage.

What tectonic plate is Maryland on? ›

Maryland, and the entire east coast of the United States, is solidly within the North American Plate. Earthquakes can and do occur within tectonic plates, but it is nowhere near as common as an earthquake occuring along the boundaries of tectonic plates, Vanko says.

What US city has the most earthquakes? ›

Los Angeles & San Francisco, United States of America

Due to its position on San Andreas fault line, California is the most earthquake-prone area of the United States.

What are the most earthquake prone areas? ›

Indonesia is in a very active seismic zone, also, but by virtue of its larger size than Japan, it has more total earthquakes. Which country has the most earthquakes per unit area? This would probably be Tonga, Fiji, or Indonesia since they are all in extremely active seismic areas along subduction zones.

What state has the most earthquakes? ›

It may come as a big surprise to the 39 million people living in California, but the state of Alaska wins the grand prize when it comes to what state has the most earthquakes. Not only is Alaska the most seismically-active state, it also is where the largest earthquake to ever strike the U.S .

What are the 5 geologic areas in Maryland? ›

Maryland is made up of six physiographic provinces, or regions where the geology and climate make the land different from adjacent areas. These provinces include the Appalachian Plateaus; Ridge and Valley; Blue Ridge; Piedmont; Atlantic Coastal Plain; and the Atlantic Continental Shelf.

Is North America Moving? ›

The North American plate is moving to the west-southwest at about 2.3 cm (~1 inch) per year driven by the spreading center that created the Atlantic Ocean, the Mid Atlantic Ridge.

What was that loud boom today 2021 Maryland? ›

A loud boom and shaking heard and felt by hundreds of residents across New Castle County Wednesday morning – which scientists initially said was an earthquake – was likely caused by a Maryland explosion, scientists now say.

What state has never had an earthquake? ›

The Answer:

According to the U.S. Geological Survey's Earthquake Information Center, every state in the U.S. has experienced an earthquake of one kind or another. It lists Florida and North Dakota as the two states with the fewest earthquakes.

Which states have very little risk of having earthquakes? ›

Is there any place in the world that doesn't have earthquakes? Florida and North Dakota are the states with the fewest earthquakes. Antarctica has the least earthquakes of any continent, but small earthquakes can occur anywhere in the World.

Will Portland be affected by the big one? ›

No! Portland is too far from the Ocean to be in danger of a tsunami. Portland, like Salem and Eugene, is in the Willamette Valley, about 60 miles from the ocean. There is a range of mountains between the valley and the ocean.

Where is safest place in earthquake? ›

Drop.

COVER your head and neck (and your entire body if possible) underneath a sturdy table or desk. If there is no shelter nearby, get down near an interior wall or next to low-lying furniture that won't fall on you, and cover your head and neck with your arms and hands.

What are the 3 most common places for earthquakes? ›

The world's 5 most earthquake-prone countries include China, Indonesia, Iran, Turkey, and Japan.

Has there ever been a 10.0 earthquake? ›

No, earthquakes of magnitude 10 or larger cannot happen. The magnitude of an earthquake is related to the length of the fault on which it occurs.

What 2 US states have the highest risk of damaging earthquakes? ›

California has more earthquakes that cause damage than any other state. Alaska and California have the most earthquakes (not human-induced).

Will we have a big earthquake soon? ›

Experts have warned for decades that a large swath of the central U.S. is at high risk for a devastating earthquake. March 3, 2022, at 3:41 p.m. ST. LOUIS (AP) — Experts have warned for decades that a large swath of the central U.S. is at high risk for a devastating earthquake.

What part of the United States is most prone to earthquakes? ›

Highest earthquake hazards in the USA are found on the west coast, the western mountain range, the midwest south of the Great Lakes, the southern coast of Alaska, and the big island of Hawaii.

Videos

1. Marylanders remember 5.8 magnitude earthquake 10 years later
(WBAL-TV 11 Baltimore)
2. Small earthquake recorded near Columbia, Maryland overnight | FOX 5 DC
(FOX 5 Washington DC)
3. Earthquake in Maryland
(Patrick Graham)
4. "It could've been worse": Residents React To Magnitude 2.6 Earthquake That Struck Woodlawn
(WJZ)
5. Earthquake caught on tape in Maryland! 8/23/11
(RakeJeed)
6. No widespread damage reported after earthquake in Maryland
(WBAL-TV 11 Baltimore)

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